every motorcycle or scooter model has it own design exhaust muffler, good quality exchaust muffler help the mtorocycle engine boot up it speed and reduce the toxci air. People now like to have modified exhaust muffler or high proformance muffler or racing exhaust on their motorycle, this would boost up motorcycle speed but also have a very strong noise effection. therefor vairous material will be use on the mufflier production, as the muffler deamds going up, there are more and more big brands come into the market, and people have more choice for their motorcycle and scooter.